1. Field of the Invention
The present invention relates to a refrigerating system provided with a Stirling refrigerating device, and to a cooling apparatus such as a refrigerator employing such a refrigerating system.
2. Description of Related Art
In general, refrigerating cycle apparatuses such as household refrigerators adopt a vapor compression refrigerating cycle using a CFC (chlorofluorocarbon) as a refrigerant. As is well known, however, CFCs are notorious for their material contribution to the destruction of the ozone layer and, from the perspective of saving the environment, their use is increasingly restricted worldwide.
In recent years, as new refrigerating technology to replace the vapor compressing refrigerating cycle, much research has been done on Stirling refrigerating devices exploiting the reversed Stirling cycle. A Stirling refrigerating device uses an inert gas such as helium as a working medium, and therefore provides a cryogenic temperature efficiently without adversely affecting the global environment.
The reversed Stirling cycle is a closed cycle in which heat rejection and heat absorption are performed by repeatedly compressing and expanding a working medium together with a displacer driven to reciprocate with a predetermined phase difference kept relative to a piston inside a single cylinder by driving the cylinder with an external force fed from a linear motor or the like.
A Stirling refrigerating device requires a means for efficiently transferring the cold obtained in a low-temperature portion, called the cold section, thereof. Moreover, the higher the refrigeration performance of the Stirling refrigerating device, the larger the amount of heat generated in a heat-rejection portion, called the warm section, thereof, and therefore, unless the generated heat is efficiently rejected, the Stirling refrigerating device shows poor refrigeration performance, producing less cold than expected in its cold section.
For example, in the Stirling refrigerator disclosed in Japanese Patent Application Laid-Open No. H7-180921, as shown in FIG. 20, a cooler 101 for cooling the interior of the refrigerator is arranged in a highest, deepest position inside the body 100 of the refrigerator, and a Stirling refrigerating device 102 is housed inside a machine compartment at the bottom of the body. The cold section 103 of the Stirling refrigerating device 102 is connected to the cooler 101 by way of a pipe 104 filled with a working medium, and the working medium is circulated so that, when the Stirling refrigerating device 102 is operated, the cold generated in the cold section 103 is transferred by the working medium to the cooler 101 placed inside the refrigerator.
Then, the cold air obtained through heat exchange taking place on the surface of the cooler 101 between the cold transferred to the cooler 101 and the air inside the refrigerator is blown into the refrigerator interior by a fan 105, so that the refrigerator interior is cooled to a predetermined temperature. On the other hand, in the warm section 106 of the Stirling refrigerating device 102, heat-rejecting fins 107 are arranged, and air is blown therethrough by a blower fan 108 to prompt heat rejection from the warm section 106.
However, while refrigeration performance of the order of a few hundred watts is required in Stirling refrigerators for which high demands are expected as models for household and commercial use, attempting to achieve such refrigeration performance with the conventional construction described above results in extremely increasing the surface area of the heat-rejecting fins 107 and the amounts of cooling air blown by the blower fan 108.
This makes the refrigerating system as a whole larger, and thus makes it necessary to secure, for the machine compartment, a volume as large as or larger than in a conventional refrigerator of the vapor compression type. This not only makes it inevitable to reduce the volume of the remaining space inside the refrigerator, but also, as a result of increased electric power consumption by the fan, degrades the efficiency of the system as a whole, contrary to energy saving.
An object of the present invention is to provide a compact Stirling refrigerating system with enhanced refrigeration efficiency achieved by prompting heat rejection from the warm section.
To achieve the above object, according to one aspect of the present invention, a Stirling refrigerating system is provided with: a Stirling refrigerating device including a piston and a displacer that reciprocate with a predetermined phase difference kept therebetween inside a cylinder having a working medium sealed therein, a heat absorber that absorbs heat from outside to produce cold as a result of the working medium being expanded in an expansion space formed inside the cylinder as the displacer reciprocates, and a heat rejecter that rejects, to outside, heat generated as a result of the working medium being compressed in a compression space formed inside the cylinder as the piston reciprocates; a ring-shaped member fitted to the heat rejecter and having a refrigerant flow passage; a cylindrical heat-rejecting heat exchanger disposed around the Stirling refrigerating device with a gap secured in between and formed so as to have a refrigerant flow passage; a refrigerant circulation passage formed by connecting the refrigerant flow passage of the ring-shaped member and the refrigerant flow passage of the heat-rejecting heat exchanger with a pipe; and circulating means for circulating a refrigerant through the refrigerant circulation passage.
Specifically, the heat-rejecting heat exchanger is composed of a first header pipe having at one end thereof a connection port to which one end of the pipe is connected, a second header pipe laid next to the first header pipe and parallel, together with the first header pipe, to the axis of the Stirling refrigerating device and having at one end thereof a connection port to which the other end of the pipe is connected, a plurality of ring-shaped condenser pipes that connect the first and second header pipes together so that they communicate with each other therethrough, and fins fitted between the plurality of condenser pipes. In this construction, the refrigerant that has collected compression heat in the compression space flows through the pipe into the second header pipe, and then flows through the ring-shaped condenser pipes into the first header pipe. Meanwhile, the compression heat is transferred to the fins, and is efficiently rejected from the surfaces of the fins. In this case, the condenser pipes and the fins may be given substantially equal lengths in the radial directions of the Stirling refrigerating device. This helps increase the surface area of the fins that contributes to heat rejection.
On the other hand, the transferring means comprises a cylindrical rod slide portion formed at the end of the Stirling refrigerating device opposite to the heat absorber, a rod slidable together with the piston along the inner surface of the rod slide portion, a first magnet fitted at the tip end of the rod, a box member fitted at the tip end of the rod slide portion and forming part of the refrigerant circulation passage, a resonant spring placed inside the box member and having the rod slide portion placed therethrough, a second magnet slidable along the outer surface of the rod slide portion by the action of the resonant spring, and a movable member fixed to the second spring and capable of reciprocating along the outer surface of the rod slide portion and along the inner surface of the box member. The refrigerant that has flowed into the box member is discharged out of it by the pumping action of reciprocating movement of the movable member.
In this construction, as the piston reciprocates, the first magnet fitted at the tip end of the rod reciprocates together, and, by the magnetism it exerts, the second magnet also reciprocates along the outer surface of the rod slide portion. Thus, the refrigerant that flows into the box member is discharged out of it by the doughnut-shaped member. This eliminates the need to use as a transferring means an external force as provided by a circulating pump or the like, and thus helps save energy.
A blower fan that blows air through the space inside the heat-rejecting heat exchanger may be provided. The air blown by the blower fan then prompts heat rejection from the surfaces of the fins of the heat-rejecting heat exchanger.
In this case, the fins may be so formed as to protrude outward from the outer profile of the condenser pipes in the radial directions. This increases, on the downstream side of the blown air, the surface area of the fins that contributes to heat rejection, and thus helps further prompt heat rejection from the fins by the blown air.
Another example of the heat-rejecting heat exchanger comprises a first header pipe having at both ends thereof connection ports that are connected to the pipe and having an internal space thereof partitioned off in a length direction thereof, a second header pipe laid next to the first header pipe and parallel, together with the first header pipe, to the axis of the Stirling refrigerating device, a plurality of ring-shaped condenser pipes that connect the first and second header pipes together so that they communicate with each other therethrough, and fins fitted between the plurality of condenser pipes.
In this construction, the refrigerant that has collected compression heat in the compression space flows through the pipe into the first header pipe, and then flows through the ring-shaped condenser pipes located on the upstream side of the partition plate into the second header pipe. Moreover, the refrigerant filling the second header pipe flows through the ring-shaped condenser pipes located on the downstream side of the partition plate back into the first header pipe. Meanwhile, the compression heat is transferred to the fins, and is efficiently rejected from the surfaces of the fins.
To achieve the above object, according to another aspect of the present invention, a Stirling refrigerating system is provided with: a Stirling refrigerating device including a piston and a displacer that reciprocate with a predetermined phase difference kept therebetween inside a cylinder having a working medium sealed therein, a heat absorber that absorbs heat from outside to produce cold as a result of the working medium being expanded in an expansion space formed inside the cylinder as the displacer reciprocates, and a heat rejecter formed as a ring-shaped refrigerant flow passage that rejects, to a refrigerant, heat generated as a result of the working medium being compressed in a compression space formed inside the cylinder as the piston reciprocates; a heat-rejecting heat exchanger disposed around the Stirling refrigerating device with a gap secured in between and formed so as to have a refrigerant flow passage; a refrigerant circulation passage formed by connecting the refrigerant flow passage of the heat rejecter and the refrigerant flow passage of the heat-rejecting heat exchanger with a pipe; and circulating means for circulating a refrigerant through the refrigerant circulation passage.
In a cooling apparatus having a Stirling refrigerating system as described above housed inside a machine compartment formed at the bottom of the body of the cooling apparatus, the interior of the body, enclosed with a heat-insulating material, is cooled by exploiting cold generated in the heat absorber as the Stirling refrigerating device is operated.